Improvement in bridges



1 Paleta.

out 'il 'may/'concern y l' l it known that I, Cuantas II. PARKER, of Bos- Bei.

v`ton, :ounty ot' Suffolk and' State of Massachusetts,

have `invented certain new and Vuseful Improvements in th Construction of Bridges; and I herebydeclare the ibllowingfto be a fulh'clear, andeXac-t description oi" the same, reference being had to the accom pan yin g Figure 1` represents aside elevation ot'a bridge made in accordance wit -`fmyvinvention.` f A Figure 2 its-'t sitleelei'ation nt' the center otthe same, on au enlarged scali. 1 n

Figure .Bre esents a vertical section ofthe bridge,

:laken.throiughtmhe point ofjunction yof ,the cantilever' and iilldependent centfeilgirder or panel.` l l The presentLiiinprovementsinbridges relate to that 'systcin ofbrdges lniown `as `tlie cantilever, the cantilever used"beingancho'red tothl-Vshore by any systcnroi'anclio age.

lheobjcctofmyintention is to -so construct a cantilever bridgclthat it willactas a cantilever` clear -to thecenter of `the span,l and thus :n'oid the ditiiculties usually experienced in this systemrof bridges, attendantupon the expansion and contraction in metallic structures, and theimpossibility of making the cantiy leverisystein available for the full length ot the span,

from fthefa'ct that a bridge composed of two-connected caniilevers cannot act as a cantilever between thc two 'pointsof'Contrai-y lcxure, but the center must act as a beam, snpportcdat its extremities upon the'cxtremel lpoints ot'the two cantilei'ews from opposite shore'.

' Another advantage `to be gained is yto free the op- ],iosite or unloudedhali' o1' a span from the eti'ect or l action of the loaded halt,

i lhjc means by which these `:ulvantages are obtained constitute the improvements in the system of the cantilever bridge, which I desire to protect -by Let-ters The manner in which these improvements are or l may be carried ont will be readily understood h v ref'- erence to the accompanying drawing.`

u 'lo"` combine the two cantilevers,'A, 'of whieh't-he `span ,is c oi'nposed,'so as to allow of ireecontraeticn or expansion away from or toward the center, the contignons ends' of the levers arenot rigidly united, but

haveja yielding connection, which, in this instance, is eii'ectfcd by means of the short center panel or girder B, the lower part ormcmber of which is, at each end, iitted into and` made Capable off-'sliding in the bottom chord of the contiguous lover;

catanese, ramener. Boston, MAssAcH j 1 'f rLetters Pateato. 103,233, dated May 17, 1870.

" The Schedule referred to: in these Letters Ptent and Imaking part of the same.

This is shown clearly in figs. 2 and V3, where the ends of the girder tit in recesses formed for their reception in the levers, and rest upon friction-,rollers a. Under this arrangement the cantlevers have no direct connection with each-other, and there is perfect freedom to contract andI expand away from and toward the center, so that eac-h' -will actas a cantilever clear to the center of thespan. v

As above stated, my furtherobject is not only to render `the ,bridge capable. of''free contract-ion and ex-V pansion 'in Athe Ymanner described, but alsol to arrange it. so that each span-will, as regards deflection, actindependently of' Athe other. This result, in part', is ef-.

fected by the ad j ustablc or yielding connection between the levers, as described, each lever beingindependent,

so that the two points of contrary eXure are removed to the center, of the span. l l Y The difference in .deflection ot' the two oantilevers, due to one of them being loaded .while the other is unloaded, I overcome by means of the short vauxiliary girder B, constructed'asbefore specified, in such lnan-V ner as to allow ot' free moveme'nt lengthwise from contraction and expansion, and hinged, at b, by bolts or other suitable means, so that a vertical movement of 4one cantilever will not be impartedto or affect the The bolts pass through slots in the bottom chords ofthe levers, as shown. in figs. 2 and 3, so that. while they hold the girderiirmly to the levers by a hinged connection', they at the same time permit thefree endwise movements of the girder or levers duelto contraction and expansion.

n Having described my invention, I would statelthat I do not claim, broadly, a bridge composed oftwo independent cantilevers connected by a central span or girdcr, as I am aware thatl the same is not new; but

What I claim, and desire to ecrire by Let-ters Patent, isa i V 1 The combination, with the two disconnected canti- Ylevers, of the auxiliary central girder,nnited withsaid levers by a hinged and sliding connection, substan-4 tially shown and setforth. l

In testimony whereof I havesi ed rny name to this spocitication befbre two subseri g g witnesses. y

l CHAS, H. PARKER.

,'Witnesses: 4

WM. A. Bhoncn'rl, CADWILLADER OURRY. 

